package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Lower-level search API. <br>
 * HitCollectors are primarily meant to be used to implement queries, sorting
 * and filtering.
 * 
 * @see Searcher#search(Query,HitCollector)
 * @version $Id: HitCollector.java 596462 2007-11-19 22:03:22Z hossman $
 */
public abstract class HitCollector {
	/**
	 * Called once for every document matching a query, with the document number
	 * and its raw score.
	 * 
	 * <P>
	 * If, for example, an application wished to collect all of the hits for a
	 * query in a BitSet, then it might:
	 * 
	 * <pre>
	 * Searcher searcher = new IndexSearcher(indexReader);
	 * final BitSet bits = new BitSet(indexReader.maxDoc());
	 * searcher.search(query, new HitCollector() {
	 * 	public void collect(int doc, float score) {
	 * 		bits.set(doc);
	 * 	}
	 * });
	 * </pre>
	 * 
	 * <p>
	 * Note: This is called in an inner search loop. For good search
	 * performance, implementations of this method should not call
	 * {@link Searcher#doc(int)} or
	 * {@link org.apache.lucene.index.IndexReader#document(int)} on every
	 * document number encountered. Doing so can slow searches by an order of
	 * magnitude or more.
	 * <p>
	 * Note: The <code>score</code> passed to this method is a raw score. In
	 * other words, the score will not necessarily be a float whose value is
	 * between 0 and 1.
	 */
	public abstract void collect(int doc, float score);
}
